Thanks for all the great advice everyone. So I'm going to:
1. inquire about orig 1855-0298 (Sphere Research, if available). per pqass
2. order a couple 2N4117 and 2N4119 (Digikey). per Flooby and Wallace
3. Try BC jcn of BC547 (I actually have some of these) and look for some low-leakage diodes on DIgik to try for kicks per Kleinstein.
Background fyi:
The 3478A was bought on the bay and seemed to be working well. A while late I noticed for the 3K ohm range, at approx 2.5-3.0K ohm load the meter read low by about 10% and was not able to successfully finish cal on the 3K ohm range.
On the 3.0K ohm range for load resistor = 0, 1, 2, 2.2, 2.5, 2.8, 3.0 K, I measured 1, 1, 1, 0.99, 0.95, 0.93, 0.85 mA, respectively, for the ohm current source (the meter read the resistor value low approx by the same %). All the other ohm ranges worked perfectly, with the current source constant over 0 to fullscale.
A shorting clip applied between Q201 emitter and CR201 anode restored the ohm current source to 1mA across the whole 3K ohm range and proper working order and successful cal. I'm guessing one of the transistors is not completely bad but is borderline, but I'm no expert

.
In the meantime I replaced the 4 Rifa caps, the 4 big electrolytic caps, and battery (temporary battery in place during R/R so as not to loose cal data). So I should be good to go shortly.
It will be a while till I get some parts but I'll let all know how it all ends up. Again big thanks for everyone's help, such a great community here.
Victor